Current-controlled CMOS logic family

ABSTRACT

Various circuit techniques for implementing ultra high speed circuits use current-controlled CMOS (C 3 MOS) logic fabricated in conventional CMOS process technology. An entire family of logic elements including inverter/buffers, level shifters, NAND, NOR, XOR gates, latches, flip-flops and the like are implemented using C 3 MOS techniques. Optimum balance between power consumption and speed for each circuit application is achieve by combining high speed C 3 MOS logic with low power conventional CMOS logic. The combined C 3 MOS/CMOS logic allows greater integration of circuits such as high speed transceivers used in fiber optic communication systems.

CROSS REFERENCE TO RELATED PATENTS/PATENT APPLICATIONS ContinuationPriority Claim, 35 U.S.C. §120

The present U.S. Utility Patent Application claims priority pursuant to35 U.S.C. §120, as a continuation, to the following U.S. Utility PatentApplication which is hereby incorporated herein by reference in itsentirety and made part of the present U.S. Utility Patent Applicationfor all purposes:

1. U.S. Utility application Ser. No. 12/789,469, entitled“Current-controlled CMOS logic family,” (Attorney Docket No. BP1645C7),filed May 28, 2010, pending, which claims priority pursuant to 35 U.S.C.§120, as a continuation, and scheduled subsequently to be issued as U.S.Pat. No. 8,299,834 on Oct. 30, 2012, (as indicated in an ISSUENOTIFICATION mailed from the USPTO on Oct. 10, 2012), to the followingU.S. Utility Patent Application which is hereby incorporated herein byreference in its entirety and made part of the present U.S. UtilityPatent Application for all purposes:

2. U.S. Utility application Ser. No. 12/784,713, entitled“Current-controlled CMOS logic family,” (Attorney Docket No. BP1645C6),filed May 21, 2010, pending, which claims priority pursuant to 35 U.S.C.§120, as a continuation, to the following U.S. Utility PatentApplication which is hereby incorporated herein by reference in itsentirety and made part of the present U.S. Utility Patent Applicationfor all purposes:

3. U.S. Utility application Ser. No. 12/363,202, entitled“Current-controlled CMOS logic family,” (Attorney Docket No. BP1645C5),filed Jan. 30, 2009, now U.S. Pat. No. 7,724,057 B2, issued on May 25,2010, which claims priority pursuant to 35 U.S.C. §120, as acontinuation, to the following U.S. Utility Patent Application which ishereby incorporated herein by reference in its entirety and made part ofthe present U.S. Utility Patent Application for all purposes:

4. U.S. Utility application Ser. No. 11/729,679, entitled“Current-controlled CMOS logic family,” (Attorney Docket No. BP1645C4),filed Mar. 29, 2007, now U.S. Pat. No. 7,486,124 B2, issued on Feb. 3,2009, which claims priority pursuant to 35 U.S.C. §120, as acontinuation, to the following U.S. Utility Patent Application which ishereby incorporated herein by reference in its entirety and made part ofthe present U.S. Utility Patent Application for all purposes:

5. U.S. Utility application Ser. No. 11/385,632, entitled“Current-controlled CMOS logic family,” (Attorney Docket No. BP1645C3),filed Mar. 21, 2006, now U.S. Pat. No. 7,215,169 B2, issued on May 8,2007, which claims priority pursuant to 35 U.S.C. §120, as acontinuation, to the following U.S. Utility Patent Application which ishereby incorporated herein by reference in its entirety and made part ofthe present U.S. Utility Patent Application for all purposes:

6. U.S. Utility application Ser. No. 11/114,969, entitled“Current-controlled CMOS logic family,” (Attorney Docket No. BP1645C2),filed Apr. 26, 2005, now U.S. Pat. No. 7,038,516 B2, issued on May 2,2006, which claims priority pursuant to 35 U.S.C. §120, as acontinuation, to the following U.S. Utility Patent Application which ishereby incorporated herein by reference in its entirety and made part ofthe present U.S. Utility Patent Application for all purposes:

7. U.S. Utility application Ser. No. 10/143,087, entitled“Current-controlled CMOS logic family,” (Attorney Docket No. BP1645C1),filed May 9, 2002, now U.S. Pat. No. 6,900,670 B2, issued on May 31,2005, which claims priority pursuant to 35 U.S.C. §120, as acontinuation, to the following U.S. Utility Patent Application which ishereby incorporated herein by reference in its entirety and made part ofthe present U.S. Utility Patent Application for all purposes:

8. U.S. Utility application Ser. No. 09/484,856, entitled“Current-controlled CMOS logic family,” (Attorney Docket No. BP1645),filed Jan. 18, 2000, now U.S. Pat. No. 6,424,194 B1, issued on Jun. 23,2002, which claims priority pursuant to 35 U.S.C. §119(e) to thefollowing U.S. Provisional Patent Application which is herebyincorporated herein by reference in its entirety and made part of thepresent U.S. Utility Patent Application for all purposes:

-   -   8.1. U.S. Provisional Application Ser. No. 60/141,355, entitled        “Current-controlled CMOS logic family,” (Attorney Docket No.        BP1645), filed Jun. 28, 1999, now expired.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates in general to integrated circuitry, and inparticular to complementary metal-oxide-semiconductor (CMOS) logic andcircuits with enhanced speed characteristics.

2. Description of Related Art

For a number of reasons CMOS is the logic family of choice in today'sVLSI devices. Due to the complementary nature of its operation, CMOSlogic consumes near zero static power. CMOS also readily scales withtechnology. These two features are highly desirable given the drasticgrowth in demand for low power and portable electronic devices. Further,with the computer aided design (CAD) industry's focus on developingautomated design tools for CMOS based technologies, the cost and thedevelopment time of CMOS VLSI devices has reduced significantly.

The one drawback of the CMOS logic family, however, remains its limitedspeed. That is, conventional CMOS logic has not achieved the highestattainable switching speeds made possible by modern sub-micron CMOStechnologies. This is due to a number of reasons. Referring to FIG. 1,there is shown a conventional CMOS inverter 100—the most basic buildingblock of CMOS logic. A p-channel transistor 102 switches between theoutput and the positive power supply Vcc, and an n-channel transistor104 switches between the output and the negative power supply (orground). The switching speed in CMOS logic is inversely proportional tothe average on resistance (Ron) of the MOS transistor, and the loadcapacitance CL on a given node (τ=Ron×C_(L). The on resistance Ron isproportional to the transistor channel length L divided by the powersupply voltage (i.e., Ron∝L/Vcc), while the load capacitance is given bythe gate capacitance of the transistor being driven (i.e., W×L×Cox,where Cox is the gate oxide capacitance), plus the interconnectparasitic capacitance C_(int). Therefore, with reduced transistorchannel lengths L, the switching speed is generally increased. However,this relationship no longer holds in sub-micron technologies. As thechannel length L in CMOS technology shrinks into the sub-micron range,the power supply voltage must be reduced to prevent potential damage tothe transistors caused by effects such as oxide breakdown andhot-electrons. The reduction of the power supply voltage prevents theproportional lowering of Ron with the channel length L. Moreover, theload capacitance which in the past was dominated by the capacitancesassociated with the MOS device, is dominated by the routing orinterconnect capacitance (C_(int)) modern sub 0.5 micron technologies.This means that the load capacitance will not be reduced in proportionwith the channel length L. Thus, the RC loading which is the main sourceof delaying the circuit remains relatively the same as CMOS technologymoves in the sub-micron range.

As a result of the speed limitations of conventional CMOS logic,integrated circuit applications in the Giga Hertz frequency range havehad to look to alternative technologies such as ultra high speed bipolarcircuits and Gallium Arsenide (GaAs). These alternative technologies,however, have drawbacks of their own that have made them more of aspecialized field with limited applications as compared to siliconMOSFET that has had widespread use and support by the industry. Inparticular, compound semiconductors such as GaAs are more susceptible todefects that degrade device performance, and suffer from increased gateleakage current and reduced noise margins. Furthermore, attempts toreliably fabricate a high quality oxide layer using GaAs have not thusfar met with success. This has made it difficult to fabricate GaAs FETs,limiting the GaAs technology to junction field-effect transistors(JFETs) or Schottky barrier metal semiconductor field-effect transistors(MESFETs). A major drawback of the bipolar technology, among others, isits higher current dissipation even for circuits that operate at lowerfrequencies.

It is therefore highly desirable to develop integrated circuit designtechniques that are based on conventional silicon CMOS technology, butovercome the speed limitations of CMOS logic.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to apparatus and methods of operationthat are further described in the following Brief Description of theSeveral Views of the Drawings, the Detailed Description of theInvention, and the claims. Other features and advantages of the presentinvention will become apparent from the following detailed descriptionof the invention made with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows a conventional CMOS inverter;

FIG. 2 is an inverter/buffer implemented in C³MOS according to anexemplary embodiment of the present invention;

FIG. 3 shows an exemplary C³MOS level shift buffer according to thepresent invention;

FIGS. 4A and 4B show exemplary C³MOS implementations for an AND/NANDgate and an OR/NOR gate, respectively;

FIG. 5 shows an exemplary C³MOS implementation for a 2:1 multiplexer;

FIG. 6 shows an exemplary C³MOS implementation for a two-input exclusiveOR/NOR gate;

FIG. 7 is a circuit schematic showing an exemplary C³MOS clocked latchaccording to the present invention;

FIG. 8 is a circuit schematic for an alternate embodiment for a C³MOSflip-flop according to the present invention;

FIG. 9 shows an exemplary C³MOS implementation for a flip-flop using theC³MOS latch of FIG. 7;

FIG. 10 shows a block diagram for a circuit that combines C³MOS andconventional CMOS logic on a single silicon substrate to achieve optimumtradeoff between speed and power consumption;

FIG. 11 shows an exemplary circuit application of the C³MOS/CMOScombined logic wherein C³MOS logic is used to deserialize and serializethe signal stream while CMOS logic is used as the core signal processinglogic circuitry;

FIG. 12 is a simplified block diagram of a transceiver system thatutilizes the C³MOS/CMOS combined logic according to the presentinvention to facilitate interconnecting high speed fiber opticcommunication channels.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides ultra high-speed logic circuitryimplemented in silicon complementary metal-oxide-semiconductor (CMOS)process technology. A distinction is made herein between the terminology“CMOS process technology” and “CMOS logic.” CMOS process technology asused herein refers generally to a variety of well established CMOSfabrication processes that form a field-effect transistor over a siliconsubstrate with a gate terminal typically made of polysilicon materialdisposed on top of an insulating material such as silicon dioxide. CMOSlogic, on the other hand, refers to the use of complementary CMOStransistors (n-channel and p-channel) to form various logic gates andmore complex logic circuitry, wherein zero static current is dissipated.The present invention uses current-controlled mechanisms to develop afamily of very fast current-controlled CMOS (or C³MOS™) logic that canbe fabricated using a variety of conventional CMOS process technologies,but that unlike conventional CMOS logic does dissipate static current.C³MOS logic or current-controlled metal-oxide-semiconductor field-effecttransistor (MOSFET) logic are used herein interchangeably.

In a preferred embodiment, the basic building block of this logic familyis an NMOS differential pair with resistive loads. Referring to FIG. 2,there is shown one embodiment for the basic C³MOS inverter/buffer 200according to the present invention. Inverter/buffer 200 includes a pairof n-channel MOSFETs 202 and 204 that receive differential logic signalsD and D# at their gate terminals, respectively. Resistive loads 206 and208 connect the drain terminals of MOSFETs 202 and 204, respectively, tothe power supply Vcc. Drain terminals of MOSFETs 202 and 204 form theoutputs OUT# and OUT of the inverter/buffer, respectively. Resistiveloads 206 and 208 may be made up of either p-channel MOSFETs operatingin their linear region, or resistors made up of, for example,polysilicon material. In a preferred embodiment, polysilicon resistorsare used to implement resistive loads 206 and 208, which maximize thespeed of inverter/buffer 200. The source terminals of n-channel MOSFETs202 and 204 connect together at node 210. A current-source n-channelMOSFET 212 connects node 210 to ground (or negative power supply). Abias voltage VB drives the gate terminal of current-source MOSFET 212and sets up the amount of current I that flows through inverter/buffer200. In response to the differential signal at D and D#, one of the twoinput n-channel MOSFETs 202 and 204 switches on while the other switchesoff. All of current I, thus flows in one leg of the differential pairpulling the drain terminal (OUT or OUT#) of the on transistor down tologic low, while the drain of the other (off) transistor is pulled up byits resistive load toward logic high. At the OUT output this circuit isa buffer, while at the OUT# output the circuit acts as an inverter.

Significant speed advantages are obtained by this type of currentsteering logic. Unlike the conventional CMOS inverter of FIG. 1, wheneither one of the input MOSFETs 202 or 204 is switching on, there is nop-channel pull-up transistor that fights the n-channel. Further, circuit200 requires a relatively small differential signal to switch itstransistors. This circuit also exhibits improved noise performance ascompared to the CMOS inverter of FIG. 1, since in the C3MOSinverter/buffer, transistors do not switch between the power supply andthe substrate. Logic circuitry based on current-steering techniques havebeen known in other technologies such as bipolar, where it is calledemitter-coupled logic (ECL), and GaAs where it is called source-coupledFET logic (SCFL). This technique, however, has not been seen in siliconCMOS technology for a number of reasons, among which is the fact thatCMOS logic has always been viewed as one that dissipates zero staticcurrent. The C³MOS logic as proposed by the present invention, on theother hand, does dissipate static current.

The design of each C³MOS logic cell according to the present inventionis optimized based on several considerations including speed, currentdissipation, and voltage swing. The speed of the logic gate isdetermined by the resistive load and the capacitance being driven. Asdiscussed above, the preferred embodiment according to the presentinvention uses polysilicon resistors to implement the load devices.P-channel MOSFETs can alternatively be used, however, they requirespecial biasing to ensure they remain in linear region. Further, thejunction capacitances of the p-channel load MOSFETs introduceundesirable parasitics. Speed requirements place a maximum limit on thevalue of the resistive loads. On the other hand, the various C³MOS logiccells are designed to preferably maintain a constant voltage swing(I×R). Accordingly, the values for R and I are adjusted based on thecapacitive load being driven to strike the optimum trade-off betweenswitching speed and power consumption.

The C³MOS logic family, according to the present invention, contains allthe building blocks of other logic families. Examples of such buildingblocks include inverters, buffers, level shift buffers, N-input NOR andNAND gates, exclusive OR (XOR) gates, flip flops and latches, and thelike. FIG. 3 shows an exemplary C³MOS level shift circuit 300 accordingto the present invention. Level shift circuit 300 includes essentiallythe same circuit elements as inverter/buffer 200 shown in FIG. 2, withan additional resistor Rs 302 inserted between the power supply Vcc andthe load resistors. Circuit 300 operates in the same fashion asinverter/buffer 200 except that it has its power supply voltage shiftedby a value equal to (I×Rs). The C³MOS logic circuitry according to thepresent invention employs this type of level shifter to make thenecessary adjustments in the signal level depending on the circuitrequirements. Examples of C³MOS circuits utilizing this type of levelshifting will be described below in connection with other types of C³MOSlogic elements.

FIGS. 4A and 4B show exemplary C³MOS implementations for an exemplary2-input AND/NAND gate 400 and an exemplary 2-input OR/NOR gate 402,respectively. These gates operate based on the same current steeringprincipal as discussed above. A logic low signal at input B of AND/NANDgate 400 brings OUT to ground via Q4 while OUT# is pulled high by itsload resistor. A logic low at the A input also pulls OUT to ground viaQ2 and Q3 (B=high). OUT is pulled high only when both A and B are highdisconnecting any path to ground. OUT# provides the inverse of OUT.OR/NOR gate 402 operates similarly to generate OR/NOR logic at itsoutputs. When another set of transistors are inserted in each leg of thedifferential pair as is the case for gates 400 and 402, the signalsdriving the inserted transistors (Q3, Q4) need level shifting to ensureproper switching operation of the circuit. Thus, high speed C³MOS levelshifters such as those presented in FIG. 3 can be employed to drivesignals B and B#. In a preferred embodiment, since node OUT in bothgates 400 and 402 must drive the additional parasitics associatedtransistors Q4, dummy load transistors DQL1 and DQL2 connect to nodeOUT# to match the loading conditions at both outputs.

FIG. 5 shows an exemplary C³MOS implementation for a 2:1 multiplexer500. Similar to the other C³MOS logic gates, multiplexer 500 includes adifferential pair for each input, but multiplexer 500 further includesselect transistors 502 and 504 inserted between the common sourceterminals of the differential pairs and the current source transistor ina cascade structure. By asserting one of the select input signals SELAor SELB, the bias current is steered to the differential pair associatedwith that select transistor. Thus, signal SELA steers the bias currentto the differential pair with A and A# inputs, and signal SELB steersthe bias current to the differential pair with B and B# inputs. Similarto gates 400 and 402, the signals SELA and SELB driving 15 insertedtransistors 502 and 504 need level shifting to ensure proper switchingoperation of the circuit.

FIG. 6 shows an exemplary C³MOS implementation for a two-input exclusiveOR (XOR) gate 600. This implementation includes two differential pairs602 and 606 that share the same resistive load, receive differentialsignals A and A# at their inputs as shown, and have their drainterminals cross-coupled at the outputs. The other differential inputsignals B and B# are first level shifted by circuit 606 and then appliedto cascade transistors 608 and 610 that are inserted between thedifferential pairs and the current source transistor. The circuit asthus constructed performs the XOR function on the two input signals Aand B.

FIG. 7 is a circuit schematic showing an exemplary C³MOS clocked latch700 according to the present invention. Latch 700 includes a firstdifferential pair 702 that receives differential inputs D and D# at thegate terminals, and a second differential pair 704 that has its gate anddrain terminals cross-coupled to the outputs of OUT and OUT# firstdifferential pair 702. Clocked transistors 706 and 708 respectivelyconnect common-source nodes of differential pairs 702 and 704 to thecurrent-source transistor. Complementary clock signals CK and CKB drivethe gate terminals of clocked transistors 706 and 708. Similar to theother C³MOS gates that have additional transistors inserted between thedifferential pair and the current-source transistor, clock signals CKand CKB are level shifted by level shift circuits such as that of FIG.3.

A C³MOS master-slave flip-flop 800 according to the present inventioncan be made by combining two latches 700 as shown in FIG. 8. A firstlatch 802 receives differential input signals D and D# and generatesdifferential output signals QI and QI#. The differential output signalsQI and QI# are then applied to the differential inputs of a second latch804. The differential outputs Q and Q# of second latch 804 provide theoutputs of flip-flop 800.

In FIG. 8, a different power supply voltage (e.g., AVDD) may be employedfor a C³MOS circuit portion than may be employed for a CMOS circuitportion (e.g., Vcc as in FIG. 1). In addition, FIG. 8 shows that yetanother, different power supply (e.g., AVSS) may be connected to thesource terminal of a current source transistor (e.g., see the currentsource transistors near the bottom of FIG. 8).

Every one of the logic gates described thus far may be implemented usingp channel transistors. The use of p-channel transistors provides forvarious alternative embodiments for C³MOS logic gates. FIG. 9 shows oneexample of an alternative implementation for a C³MOS clocked latch 900that uses p-channel transistors. In this embodiment, instead ofinserting the n-channel clocked transistors between the common-sourcenodes of the differential pairs and the current-source transistor, pchannel clocked transistors 902 and 904 connect between thecommon-source nodes and the power supply Vcc. This implementation alsorequires that each differential pair have a separate current-sourcetransistor as shown. Clocked latch 900 operates essentially the same aslatch 700 shown in FIG. 7, except the implementation is not as efficientboth in terms of size and speed.

As illustrated by the various C³MOS logic elements described above, allof the building blocks of any logic circuitry can be constructed usingthe C³MOS technique of the present invention. More complex logiccircuits such as shift registers, counters, frequency dividers, etc.,can be constructed in C³MOS using the basic elements described above. Asmentioned above, however, C³MOS logic does consume static power. Thestatic current dissipation of C³MOS may become a limiting factor incertain large scale circuit applications. In one embodiment, the presentinvention combines C³MOS logic with conventional CMOS logic to achievean optimum balance between speed and power consumption. According tothis embodiment of the present invention, an integrated circuit utilizesC³MOS logic for the ultra high speed (e.g., GHz) portions of thecircuitry, and conventional CMOS logic for the relatively lower speedsections. For example, to enable an integrated circuit to be used inultra high speed applications, the input and output circuitry thatinterfaces with and processes the high speed signals is implementedusing C³MOS. The circuit also employs C³MOS to divide down the frequencyof the signals being processed to a low enough frequency whereconventional CMOS logic can be used. The core of the circuit, accordingto this embodiment, is therefore implemented by conventional CMOS logicthat consumes zero static current. FIG. 10 shows a simplified blockdiagram illustrating this exemplary embodiment of the invention. A C³MOSinput circuit 1000 receives a high frequency input signal IN and outputsa divided down version of the signal IN/n. The lower frequency signalIN/n is then processes by core circuitry 1002 that is implemented inconventional CMOS logic. A C³MOS output circuit 1004 then converts theprocessed IN/n signal back to the original frequency (or any otherdesired frequency) before driving it onto the output node OUT.

An example of a circuit implemented using combined CMOS/C³MOS logicaccording to the present invention is shown in FIG. 11. C³MOS inputcircuitry 1100 is a deserializer that receives a serial bit stream at ahigh frequency of, for example, 2 GHz. A 2 GHz input clock signal CLK isdivided down to 1 GHz using a C³MOS flip-flop 1102, such as the oneshown in FIG. 8, that is connected in a ÷2 feedback configuration. The 1GHz output of flip-flop 1102 is then supplied to clock inputs of a pairof C³MOS latches 1104 and 1106. Latches 1104 and 1106, which may be ofthe type shown in FIG. 6, receive the 2 GHz input bit stream at theirinputs and respectively sample the rising and falling edges of the inputbit stream in response to the 1 GHz clock signal CLK/2. The signal CLK/2which is applied to the B/B# inputs of each latch (the level shiftedinput; see FIG. 6), samples the input data preferably at its center. Itis to be noted that the rise and fall times of the signal in CMOS logicis often very dependent on process variations and device matching. C³MOSlogic, on the other hand, is differential in nature and thereforeprovides much improved margins for sampling.

Referring back to FIG. 11, block 1100 thus deserializes the input bitstream with its frequency halved to allow for the use of conventionalCMOS logic to process the signals. The signals at the outputs of latches1104 and 1106 are applied to parallel processing circuitry 1108 that areimplemented in conventional CMOS logic operating at 1 GHz. The reverseis performed at the output where a serializer 1110 receives the outputsignals from processing circuitry 1108 and serializes them using C³MOSlogic. The final output signal is a bit stream with the original 2 GHzfrequency. Circuit applications wherein this technique can beadvantageously employed include high speed single or multi-channelserial links in communication systems.

As apparent from the circuit shown in FIG. 11, this technique doublesthe amount of the core signal processing circuitry. However, since thispart of the circuit is implemented in conventional CMOS logic, currentdissipation is not increased by the doubling of the circuitry. Thoseskilled in the art appreciate that there can be more than one level ofdeserializing if further reduction in operating frequency is desired.That is, the frequency of the input signal can be divided down furtherby 4 or 8 or more if desired. As each resulting bit stream will requireits own signal processing circuitry, the amount and size of the overallcircuitry increases in direct proportion to the number by which theinput signal frequency is divided. For each application, therefore,there is an optimum number depending on the speed, power and arearequirements.

According to one embodiment of the present invention the combinedC³MOS/CMOS circuit technique as shown in FIG. 11 is employed in atransceiver of the type illustrated in FIG. 12. The exemplarytransceiver of FIG. 12 is typically found along fiber optic channels inhigh speed telecommunication networks. The transceiver includes at itsinput a photo detect and driver circuit 1200 that receives the inputsignal from the fiber optic channel. Circuit 1200 converts fiber-opticsignal to packets of data and supplies it to a clock data recovery (CDR)circuit 1202. CDR circuit 1202 recovers the clock and data signals thatmay be in the frequency range of about 2.5 GHz, or higher. Establishedtelecommunication standards require the transceiver to perform variousfunctions, including data monitoring and error correction. Thesefunctions are performed at a lower frequency. Thus, the transceiver usesa demultiplexer 1204 which deserializes the 2.5 GHz data stream into,for example, 16 parallel signals having a frequency of about 155 MHz. Anapplication specific integrated circuit (ASIC) 1206 then performs themonitoring and error correction functions at the lower (155 MHz)frequency. A multiplexer and clock multiplication unit (CMU) 1208converts the parallel signals back into a single bit stream at 2.5 GHz.This signal is then retransmitted back onto the fiber optic channel by alaser drive 1212. The combined C³MOS/CMOS technique of the presentinvention allows fabrication of demultiplexer 1204, ASIC 1206 andmultiplexer and CMU 1208 on a single silicon die, as indicated byreference numeral 1210, in a similar fashion as described in connectionwith the circuit of FIGS. 10 and 11. That is, demultiplexer 1204 andmultiplexer and CMU 1208 are implemented in C³MOS with ASIC 1206implemented in conventional CMOS.

In conclusion, the present invention provides various circuit techniquesfor implementing ultra high speed circuits using current-controlled CMOS(C³MOS) logic fabricated in conventional CMOS process technology. Anentire family of logic elements including inverter/buffers, levelshifters, NAND, NOR, XOR gates, latches, flip-flops and the like havebeen developed using C³MOS according to the present invention. In oneembodiment, the present invention advantageously combines high speedC³MOS logic with low power conventional CMOS logic. According to thisembodiment circuits such as transceivers along fiber optic channels canbe fabricated on a single chip where the ultra-high speed portions ofthe circuit utilize C³MOS and the relatively lower speed parts of thecircuit use conventional CMOS logic. While the above is a completedescription of the preferred embodiment of the present invention, it ispossible to use various alternatives, modifications and equivalents.Therefore, the scope of the present invention should be determined notwith reference to the above description but should, instead, bedetermined with reference to the appended claims, along with their fullscope of equivalents.

In addition, certain embodiments of the present invention provide a newfamily of CMOS logic that is based on current-controlled mechanism tomaximize speed of operation. The current-controlled CMOS (or C³MOS™)logic family according to the present invention includes all thebuilding blocks of any other logic family. The basic building block ofthe C³MOS logic family uses a pair of conventional MOSFETs that steercurrent between a pair of load devices in response to a differencebetween a pair of input signals. Thus, unlike conventional CMOS logic,C³MOS logic according to this invention dissipates static current, butoperates at much higher speeds. In one embodiment, the present inventioncombines C³MOS logic with CMOS logic within the same integratedcircuitry, where C³MOS is utilized in high speed sections and CMOS isused in the lower speed parts of the circuit.

Accordingly, in one embodiment, the present invention provides acurrent-controlled metal-oxide semiconductor field-effect transistor(MOSFET) circuit fabricated on a silicon substrate, including a clockedlatch made up of first and second n-channel MOSFETs having their sourceterminals connected together, their gate terminals coupled to receive apair of differential logic signals, respectively, and their drainterminals connected to a true output and a complementary output,respectively; a first clocked n-channel MOSFET having a drain terminalconnected to the source terminals of the first and second n-channelMOSFETs, a gate terminal coupled to receive a first clock signal CK, anda source terminal; third and fourth n-channel MOSFETs having theirsource terminals connected together, their gate terminals and drainterminals respectively cross-coupled to the true output and thecomplementary output; a second clocked n-channel MOSFET having a drainterminal connected to the source terminals of the third and fourthn-channel MOSFETs, a gate terminal coupled to receive a second clocksignal CKB, and a source terminal; first and second resistive elementsrespectively coupling the true output and the complementary output to ahigh logic level; and a current-source n-channel MOSFET connectedbetween the source terminals of the first and second clocked n-channelMOSFETs and a logic low level.

In another embodiment, the circuit further includes a buffer/invertermade up of first and second n-channel MOSFETs having their sourceterminals connected together, their gate terminals respectively coupledto receive a pair of differential logic signals, and their drainterminals coupled to a high logic level via a respective pair ofresistive loads; and a current-source n-channel MOSFET connected betweenthe source terminals of the first and second n-channel MOSFETs and a lowlogic level, wherein, the drain terminal of the first n-channel MOSFETprovides a true output of the buffer/inverter and the drain terminal ofthe second n-channel MOSFET provides the complementary output of thebuffer/inverter.

In yet another embodiment, the present invention provides complementarymetal-oxide-semiconductor (CMOS) logic circuitry that combines on thesame silicon substrate, current-controlled MOSFET circuitry of the typedescribed above for high speed signal processing, with conventional CMOSlogic that does not dissipate static current. Examples of such combinedcircuitry include serializer/deserializer circuitry used in high speedserial links, high speed phase-locked loop dividers, and the like.

1. An apparatus, comprising: a first circuit block to receive an inputsignal from a communication channel and to generate a serialized signal;and a second circuit block, including current-controlled complementarymetal-oxide semiconductor (C³MOS) logic, to deserialize the serializedsignal to generate a deserialized signal including a plurality ofsignals; a third circuit block, coupled to the second circuit block andincluding conventional complementary metal-oxide-semiconductor (CMOS)logic wherein substantially zero static current is dissipated, toprocess the plurality of signals to generate a plurality of processedsignals; and wherein: the C³MOS logic including a first metal-oxidesemiconductor (MOS) transistor with a first drain, a first gate, and afirst source and a second MOS transistor with a second drain, a secondgate, and a second source such that a current steering circuit withinthe C³MOS circuit including the first source and the second source; thefirst source and the second source being coupled together and to acurrent source; and the first drain and the second drain being coupledto a power supply.
 2. The apparatus of claim 1, wherein: the serializedsignal and the plurality of signals being electrical signals includingdata compliant with a fiber channel.
 3. The apparatus of claim 1,wherein: the first circuit block including at least one circuit toreceive the input signal from the communication channel and to generatethe serialized signal; and the second circuit block being an integratedcircuit or implemented on a single silicon die.
 4. The apparatus ofclaim 1, wherein: the second circuit block included within an integratedcircuit; and the serialized signal being provided to the integratedcircuit from off-chip.
 5. The apparatus of claim 1, wherein: the firstcircuit block including a photo detect and driver circuit to receive theinput signal received from a fiber optic channel and to generate aplurality of packets of data; and the first circuit block also includinga clock data recovery (CDR) circuit to process the plurality of packetsof data to generate the serialized signal.
 6. The apparatus of claim 1,wherein: the CMOS logic being coupled to a first power supply; and theC³MOS logic being coupled to a second power supply.
 7. The apparatus ofclaim 1, wherein: the second circuit block including a C³MOS clockedlatch or a C³MOS master-slave flip-flop including a plurality oflatches.
 8. An apparatus, comprising: a first circuit block to receivean input signal from a communication channel and to generate aserialized signal; and a second circuit block, includingcurrent-controlled complementary metal-oxide semiconductor (C³MOS)logic, to process the serialized signal; a third circuit block, coupledto the second circuit block and including conventional complementarymetal-oxide-semiconductor (CMOS) logic wherein substantially zero staticcurrent is dissipated, to receive a processed version of the serializedsignal; and wherein: the C³MOS logic including a first metal-oxidesemiconductor (MOS) transistor with a first drain, a first gate, and afirst source and a second MOS transistor with a second drain, a secondgate, and a second source such that a current steering circuit withinthe C³MOS circuit including the first source and the second source; thefirst source and the second source being coupled together and to acurrent source; and the first drain and the second drain being coupledto a power supply.
 9. The apparatus of claim 8, wherein: the secondcircuit block included within an integrated circuit; and the serializedsignal being provided to the integrated circuit from off-chip.
 10. Theapparatus of claim 8, wherein: the input signal and the serializedsignal being electrical signals including data compliant with a fiberchannel.
 11. The apparatus of claim 8, wherein: the CMOS logic beingcoupled to a first power supply; and the C³MOS logic being coupled to asecond power supply.
 12. An apparatus, comprising: a first circuit blockto provide a serialized signal; and a second circuit block, includingcurrent-controlled complementary metal-oxide semiconductor (C³MOS)logic, to process the serialized signal; and wherein: the C³MOS logicincluding a first metal-oxide semiconductor (MOS) transistor with afirst drain, a first gate, and a first source and a second MOStransistor with a second drain, a second gate, and a second source suchthat a current steering circuit within the C³MOS circuit including thefirst source and the second source; the first source and the secondsource being coupled together and to a current source; and the firstdrain and the second drain being coupled to a power supply.
 13. Theapparatus of claim 12, wherein: the first circuit block including atleast one circuit to receive an input signal from a communicationchannel and to generate the serialized signal.
 14. The apparatus ofclaim 12, wherein: the first circuit block including a photo detect anddriver circuit to receive an input signal received from a fiber opticchannel and to generate a plurality of packets of data; and the firstcircuit block also including a clock data recovery (CDR) circuit toprocess the plurality of packets of data to generate the serializedsignal; and the input signal and the serialized signal being electricalsignals including data compliant with a fiber channel.
 15. The apparatusof claim 12, wherein: the first circuit block including at least onecircuit to receive an input signal from a communication channel and togenerate the serialized signal; and the second circuit block being anintegrated circuit or implemented on a single silicon die.
 16. Theapparatus of claim 12, wherein: the second circuit block being anintegrated circuit; and the serialized signal being provided to theintegrated circuit from off-chip.
 17. The apparatus of claim 12,wherein: the second circuit block to deserialize a serialized signal togenerate a deserialized signal including a plurality of signals.
 18. Theapparatus of claim 12, further comprising: a third circuit block,coupled to the second circuit block and including conventionalcomplementary metal-oxide-semiconductor (CMOS) logic whereinsubstantially zero static current is dissipated, to receive a processedversion of the serialized signal.
 19. The apparatus of claim 18,wherein: the CMOS logic being coupled to a first power supply; and theC³MOS logic being coupled to a second power supply.
 20. The apparatus ofclaim 12, wherein: the second circuit block including a C³MOS clockedlatch or a C³MOS master-slave flip-flop including a plurality oflatches.